The present invention relates to a shear for cutting moving bars (strips) with two counter-rotating knife drums rotating in shear stands. The spaced shear stands are located on a base plate, and are connected with each other by a disconnectable yoke.
The shears before the last station of belt conveyers have the task of cropping the bars entering the last station at the front and rear end. They are preferably designed as drum shears. The drum shears are mounted in mountings which are held by shear stands with removable stand heads; the shear stands are connected above the knife shafts via a disconnectable yoke. Outside the shear stand, the knife shafts are connected with one another by a broad-faced gear. The drive operates via the lower knife shaft. The shear knife is replaced on the spot. With straight knives, it takes approximately two hours. With curved knives this time is increased to three hours when a pair of knives is used for the forward and rear cut. If plates or sheets are to be cut at the forward and rear end in opposite directions so that two pairs of knives are required, knife replacement takes six hours. The shear knives are replaced selectively in planned intervals. It frequently happens that with knife breakage the entire rolling mill must be stopped for a knife replacement. If it is necessary that the knife shafts or the inserts must be replaced, 36- 48 hours are required. A knife shaft replacement always causes an extended stoppage, since stoppages of 36-48 hours cannot be included in the schedule.
In order to reduce the duration of stoppages, particularly for replacing the knife shafts, it has been proposed that the upper and lower knife shaft be mounted in common mountings. Again the replacement time is too long, because the replacement time is still 12 hours or more.
With another known shear design, the knife shafts with the mountings can be pulled out sideways from the shear stand. This reduces knife replacement to approximately 30 minutes if it can be planned. The shear is still built very expensively. The scrap removal is greatly impeded at times. An unplanned knife shaft replacement still takes approximately 90 minutes.
Accordingly, it is an object of the present invention to avoid the disadvantages of known devices or drum shears and to provide a shear with knife drums mounted in shear stands; this reduces the interference (down) times resulting from replacing the shear knives or knife drums to a minimum.
Another object of the present invention is to provide a shearing arrangement of the foregoing character which is substantially simple in construction and may be economically fabricated.
A further object of the present invention is to provide a shearing arrangement, as described, which may be readily maintained in service, and which has a substantially long operating life.